1. Technical Field
This invention relates to fasteners, bolts and threaded plugs, and mechanisms for sealing the bolt holes or plug holes.
2. Background
Threaded bolts and threaded plugs used in piping and equipment in high pressure service typically require use of a loose gasket between the bolt head and the piping or equipment. The gasket helps seal the holes and prevent leakage of high pressure material from around the threads of the bolts or plugs. A common service for gaskets and threaded plugs is on the tube sheet header of fin fan exchangers in chemical plants. Existing plug gaskets include flat soft metal ring, or a flat metal ring sandwiched between two sheets of flexible graphite over each side. The flat metal ring may have concentric grooving on both sides surfaced with graphite or PTFE to form a covered serrated metal gasket, also known as a Kammprofile gasket. The DIN EN 1514-6 Standard describes details of such gaskets.
The costs associated with the use of conventional loose gaskets are not minimal. Significant time and labor costs may be incurred to ensure proper seating of the loose gasket on the bolt or plug before fastening. The gaskets may be over compressed resulting in damage to the gasket requiring its replacement, or in severe instances, damage to the equipment in contact with the gasket. The costs for purchasing the gaskets in large volumes add up. The costs for inventory and control of different size gaskets and matching them with the correct size bolt or plug also add up. Therefore, it may be desirable to have an improved design for a gasket that costs less and requires less labor to install.